Field of the Invention and Brief Description of Prior Art
The invention concerns a transducer insert. The invention also concerns a method for making the transducer insert and also a sensor for measuring mechanical variables using such transducer insert.
The invention generally relates to electro-mechancial sensors, where a change in force introduced from outside is transformed into a change in resistance or capacitance generating a corresponding electrical signal.
Generally speaking, there is little space available for this type of sensor at the measuring point, so that today, the use of small semi-conductor sensors having high sensitivity is preferred. This type of sensor can be exposed to difficult environmental conditions in its place of use, such as very high or low temperatures, essential temperature fluctuations, high humidity, agressive media, high and even radioactive radiation and also magnetic and electrical fields. Particular problems are caused by oscillations and shocks. The Ball-Bond and Wedge-Bond techiques using fine gold wires, as generally used in semi-conductor technology, are susceptible to faults as they follow the oscillation and shock movements, which can lead to fatigue fractures and/or breaking of these connections. Examples of such prior bonding technique are shown in FIGS. 1-3 and will be explained later.
Reference is also made to the following U.S. Pats. Nos.: 3,838,379, 3,654,579, 4,412,203, 4,454,771 which describe pressure transducers of the type employing semi-conductor devices and wire or rod-like conductor elements for carrying off the measuring signals.
European Pat. application, publication No. 0 024 946, describes a capacitance transducer and a method for its manufacture using batch-processing techniques. The transducer comprises a semi-conductor body and a glass body having electrically conductive elektrode areas forming a capacitance. A plurality of holes penetrate the glass body. The holes are coated with films of conductive material which simply contact the electrically conductive elektrode areas of the semi-conductor and glass bodies to provide electrical contact therewith. Such connections have inferior strength and are susceptible to premature fatigue when exposed to shock or vibration stresses. Another disadvantage is that the quality of the connection cannot be readily checked at the finished product.